Automatic choke control and air preheater



y 1961 J o. SARTO 2,992,641

AUTOMATIC CHOKE CONTROL AND AIR PREHEATER 7 Filed July 15, 1960 2 Sheets-Sheet 1 INVENTOR. for/17.4 0. 54 12 0.

July 18, 1961 J. o. SARTO AUTOMATIC CHOKE CONTROL AND AIR PREHEATER Filed July 15, 1960 2 Sheets-Sheet 2 KM W R m m m JZrma 0, 541*2 A mm MW fiTTOF/VEYS United States Patent 9 i 2,992,641 AUTOMATIC CHOKE CONTROL AND AIR PREI EATER Jorma O. Sarto, Orchard Lake, Mich., assignor to Chrysler Corporation, Highland Park, Mich., a corporation of Delaware Filed July 15, 1960, Ser. No. 43,203 12 Claims. (Cl. 123-419) This invention relates to a fuel system for an internal combustion engine and in particular to means for matching the temperature and volume of the combustion supporting air flow with the engine temperature so as to achieve optimum operating efficiency.

In a customary water cooled automobile engine, cooling water is circulated through a coolant duct system in the walls of the engine and thence to a radiator or heat exchanger which dissipates the heat of the cooling water to the atmosphere and to an inlet supply of combustion supporting air to preheat the latter. The preheated air is then directed to the engine via an air inlet or induction conduit controlled by a choke valve which is regulated automatically in response to the engine temperature indicated either by the temperature of engine coolant circulating in the Walls of the engine, or the engine exhaust gases. In order to assure rapid warming of the engine during its initial stages of operation, a thermostatically controlled valve is interposed between the engine coolant duct system and the radiator, the valve being normally closed until the engine temperature rises to a predetermined operating condition.

In such constructions, while the engine is cold, the choke valve is yieldingly biased resiliently toward a closed position to assure the supply of a comparatively rich fuelair mixture to the engine. Coupled with the thermostatically controlled choke valve is a fast idle cam which holds the throttle valve open slightly during cold engine idling. As the engine is progressively heated, the choke valve is enabled to open progressively to supply a leaner fuel-air mixture to the engine, and the fast idle cam moves out of contact with the throttle to reduce the engine idle speed.

During cold weather and particularly during humid weather at temperatures approximating 40 F., the engine temperature tends to open the choke valve several minutes before the radiator or heat exchanger is heated to substantially its equilibrium condition. In consequence, the choke valve opens to provide a comparatively lean fuel-air mixture several minutes before the incoming combustion supporting air supply through the radiator is preheated to the desired temperature corresponding to the position of the choke valve. Poor engine operation and throttle icing frequently result.

Prior to opening of the choke valve and movement of the fast idle cam out of contact with the throttle, the latter is held open suificiently by the fast idle cam so that icing, if it occurs, ordinarily does not completely block the throttle controlled inlet passage and is not particularly objectionable. However, between the time that the engine temperature rises sutliciently to enable the fast idle cam to ride out of contact with the throttle, and the time that the radiator is heated approximately to its equilibrium temperature so as to preheat the inlet air to a temperature matching the extent of the choke valve opening, icing can be objectionable and engine stalling at idle speeds can be objectionable. After a few miles of driving, the radiator will attain its equilibrium temperature and the incoming combustion supporting air supply will be adequately preheated to match the choke valve position. The engine will then operate substantially as desired in accordance with its design.

Patented July 18, 1961 An important object of the present invention is to provide improved means for matching the position of a thermostatically operated choke valve of a carburetor for an automobile engine with the temperature of the inlet combustion supporting air so as to obtain improved cold weather engine operation between the time following the initial warm-up of the engine and the time required for the customary radiator to preheat the inlet combustion supporting air to 'a temperature matching the choke valve position as determined by the engine temperature.

Another object is to provide such a construction including an engine fluid coolant duct system having a hot fluid outlet connected by a coupling conduit with the radiator, the cooled fluid being discharged from the radiator to the inlet side of the coolant duct system. A thermostatically controlled coolant valve normally closes the outlet of the coolant duct system to the aforesaid coupling conduit, when the engine is cold, and is responsive to the temperature of the heated coolant upstream of the coupling conduit to open the connection between the coolant duct system and the radiator as the temperature of the engine progressively rises. An air heating duct having an opening for receiving fresh combustion supporting air also has a portion within. said coupling conduit in heat exchange relationship therewith downstream of the coolant valve to heat the air in said heating duct. The heated air from the latter duct is then conveyed first to the temperature responsive element for the choke valve to heat the same and relax the resilient biasing force urging the choke valve to its closed position. Thereafter the heated air from the heating duct is admixed with the main supply of combustion supporting air to preheat the latter and facilitate vaporization of liquid fuel prior to combustion of the fuel-air mixture in the engine.

By virtue of the foregoing structure, heating of the choke valve thermostat is delayed until after the initial engine warmup has progressed sutficiently to open the coolant valve to the radiator. In consequence the carburetor choke valve will remain substantially at its cold setting determined by the ambient air temperature until after the coolant valve to the radiator opens. When the choke valve does eventually begin to open, a portion of the combustion air supply will be at the same temperature as the temperature to which the choke thermostat is responsive. Thus an initial air preheating occurs, icing is minimized, and opening of the choke valve is more accurately matched with the temperatures of both the inlet air and the engine.

Preferably the resistance of the air heating duct is predetermined so that the latter will supply between approximately 10-15% and preferably about 12% of the total inlet combustion supporting air while the engine is idling, thereby to achieve optimum operation of the carburetor Without necessitating a redesign of its customary fuel and air supply characteristics.

Still another object is to provide such a structure wherein the cooled coolant from the radiator is discharged to the inlet side of an engine driven coolant pump arranged in the inlet of the engine coolant duct system to cause circulation of pressurized coolant therein. A restricted bypass for the pump connem the outlet of the coolant duct system with the pump inlet to enable a limited circulation of coolant within the coolant duct system prior to opening of the coolant valve to the radiator.

Another object is to provide an improved automatic thermostatic choke valve control and preheater for the inlet combustion supporting air, which is particularly adapted for use with a water cooled aluminum engine. Accordingly superior cold weather operation is achieved during the warmup stages of such an aluminum engine which is not susceptible of choke regulation by exhaust gas heat without additional costly temperature regulation. Otherwise, unless the exhaust heat supply to the temperature responsive element of the choke valve is regulated, the aluminum material of the engine is subject to overheating and damage by the exhaust heat.

Other objects of this invention will appear in the following description and appended claims, reference being had to the accompanying drawings forming a part of this specification wherein like reference characters designate corresponding parts in the several views.

FIGURE 1 is a schematic side elevational view of an automobile engine with portions broken away to illust-rate details of the invention.

FIGURE 2 is an enlarged fragmentary sectional view taken in the direction of the arrows substantially along the line 22 of FIGURE 1.

FIGURE 3 is an enlarged vertical sectional view through the carburetor embodying the present invention, showing the connection between the inlet air induction conduit and the air heating duct.

FIGURE 4 is a fragmentary vertical mid-sectional view through the thermostatic coolant valve, showing a modification.

It is to be understood that the invent-ion is not limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawings, since the invention is capable of other embodiments and of being practiced or carried out in various ways. Also it is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation.

Referring to the drawings, a particular embodiment of the present invention is illustrated by Way of example comprising a water cooled automobile engine 10, which may be of cast aluminum, having an engine driven shaft 11 on which is keyed a rotatable pulley 12. A fan belt 13 connects the pulley 12 with the pulley 14 of a fan 15 to drive the latter. In the present instance, the fan pulley 14 also drives a coaxial shaft 16 of a water pump 17 mounted within the body of the engine 10. The water pump 17 is located in the inlet of an engine coolant duct system "18 so as to circulate a fluid coolant such as Water through the system 18 under pressure. The outlet of the duct system 18 is connected by an upper coupling hose 19 with the hot or inlet side of a conventional radiator or heat exchanger 20 having a foraminous core for passage of air therethrough in the direction of the arrows 20a in heat exchange relationship. In operation, hot water is circulated through the radiator 20 from hose 19 and is thus cooled by the air flow 20a. The cooled water is returned to the inlet of the pump 17 by means of a return conduit 21. In cooling the water flow through radiator 20, the air flow "Ztla is heated, a portion of which is directed under the customary engine hood to the carburetor air inlet to support fuel combustion in the engine.

Downstream of the outlet of the engine coolant duct system 18 is a thermostatically controlled coolant valve 22 in hose 19 having its temperature responsive element 22a adjacent the outlet of the duct system 18 at a location upstream of the valve 22. In order to enable limited circulation of coolant within the system 18 when the valve 22 is closed, a restricted bypass 23 is provided between the outlet of duct system 18 and the inlet to pump 17.

Mounted above the engine in the customary manner, is a carburetor 24 having an air inlet induction conduit 25, FIGURE 3, which receives combustion supporting air at its upper end from the air flow 20a that has passed through radiator 20 and discharges the air and fuel to the engine in a manner well known to the art. The upper inlet of conduit 25 is preferably provided with an air filter, not shown. The conduit 25 is also suitably provided with an upper choke valve 26 and a lower throttle valve 27 The choke valve 26 in the present instance is of the unbalanced butterfly type suitably secured to a pivotal shaft 28 journalled in the body of the carburetor 24. The left end of shaft 28 is keyed to a lever 29 for actuation thereby, the latter in turn being suitably secured to the free end of a spiral bimetallic thermostat element 30 having a fixed "end mounted on a central fixed hub shaft 31. The shaft 31 as well as the thermostatic element 30 and lever 29 are enclosed within a hollow container 32 suitably secured to the body of the carburetor 24. A duct 33 within the carburetor body connects the interior of container 32 with the induction conduit 25 at a location downstream of throttle valve 27. Preferably duct 33 is restricted at 33a to provide a controlled air flow therethrough.

An air preheating conduit is provided with an opening 34 immediately rearward of fan 15 and confronting the latter to receive air therefrom. The opening 34 is preferably provided with an air filter to prevent dirt from entering the fuel system. The air heating duct also includes a U-shaped portion 35 within the hose 19 in heat exchange relationship with the coolant therein at a location downstream of valve 22. Exteriorly of hose 19, the heating duct comprises an insulated portion 36 connected by means of a coupling 37 with the side wall of container 32. A duct 38 in the latter communicates with the interior of the air heating duct 35, 36 and directs hot air from the latter as explained below to the coils of the thermostatic element 30.

With the exception of the air heating duct 35, 36 and specific details of the container 32 and conduit 33, the carburetor may be conventional and includes the usual fuel bowl 39 from which fuel is supplied into the induction conduit 25 via metering orifice 4t duct 41 and nozzle 42. As illustrated, nozzle 42 opens into the induction conduit 25 at the region of a restricted venturi 43 so as to enhance the responsiveness of its fuel discharge in accordance with the rate of air flow in the conduit 25 as determined by the opening of the throttle and choke valves 27 and 26.

Throttle valve 27 may be manually controlled, whereas choke valve 26 is controlled both by the air flow in conduit 25 and the resilient biasing force of thermostatic element 30. The latter when cold is normally operative to urge choke valve 26 yieldingly to a closed position, and will yield resiliently to enable opening of the valve 26 with increased air flow through the conduit 25 resulting from opening of valve 27 As the temperature of element 30 increases, its resilient tension normally urging choke valve 26 to the closed position relaxes, so that opening of the latter will increase for any given rate of air flow in conduit 25.

Also opening downstream of throttle valve 27 adjacent the outlet of duct 33 is a conventional idle bleed port 44 connected by duct 45 in the sidewall of carburetor 24 with duct 41 to supply fuel to the engine during idle conditions. Extending both above and below the upper edge of throttle valve 27 when the latter is in its closed position is a conventional elongated transfer port 46 which opens through the sidewall of conduit 25 and communicates with duct 45. The latter is provided with an upper restricted vent opening 47 opening into the induction conduit 25 and is also connected with fuel conduit 41 by restricted idle bleed duct 48 in the sidewall of carburetor 24, the duct 48 being restricted at 49, all in a manner well known to the art.

In accordance with the structure described, when the engine is idling in a cold condition, the thermostatic element 22a will urge valve 22 to the closed position to prevent flow of coolant in conduit 19. In consequence, operation of pump 17 will circulate cooling water through the duct system 18 and thence via bypass 23 to the pump inlet. Air is drawn through radiator 20 in the direction of the arrows 20a by operation of fan 15 and is forced into the opening 34 of duct 35, 36, then via coupling 37 and duct 38 to the interior of container 32 where the air is circulated through the coils of the thermostat element 30, and then via duct 33 into induction conduit 25 to adrnix with and help vaporize the idle fuel supplied through port 44.

At this time, by reason of valve 22 being closed, there is no circulation of coolant in hose 19 and radiator 20, and the air being supplied to the thermostat element 30 via duct 35, 37 will be at the ambient temperature. During cold ambient conditions, the thermostat element 30 will yieldingly urge choke valve 26 toward its closed position to insure an enriched fuel-air supply to the engine in accordance with the temperature of the ambient air.

As the engine begins to Warm and the coolant within the duct system 18 is heated, thermostatic valve 22 will gradually open to enable circulation of the heated coolant through hose 19 and thence through radiator 20. Only then will the air flowing through duct 35, 36 be heated so as to Warm thermostat element 30. In consequence, during operation of the engine at cold ambient air temperatures the thermostat element 30 will tend to urge choke valve 26 to its closed position until after the opening of valve 22 to allow circulation of the heated coolant through radiator v20. Thereafter the air passing through radiator 20 will be heated by the latter to supply preheated air to the inlet of the carburetor induction conduit 25, so that the temperature of the preheated combustion supporting air will closely match the setting of the choke valve as determined by the thermostatic element 30.

In the usual operation of valve 22, the latter will remain completely closed until the thermostat element 22a is actuated by the temperature of coolant in duct system 18 greater than a predetermined minimum. In consequence, during operation of the engine from a cold start, the air inlet manifold 50, FIGURE 1, which may be of aluminum construction and which receives the fuel-air mixture from conduit 25, will be heated by the engine somewhat before the coolant in duct system 18 heats sufficiently to open valve 22. During this period of operation, the inlet air passing through manifold 50 will be heated to a temperature in excess of that required for the choke setting determined by the cold ambient air acting on thermostat element 30, with the result that the fuelair mixture to the engine will be richer than necessary for efficient and economical operation.

The foregoing problem can be avoided by providing a temperature responsive valve 22 which will progressively open to enable a progressive heating of the inlet air passing through heating duct 35, starting with the initial heating of the coolant in duct 18. However the provision of such a valve that would assure the desired temperature controlled flow of coolant into hose 19 during the comparatively small initial temperature changes involved would be costly. It is accordingly within the concept of the present invention to provide a controlled bypass for valve 22, as for example a valve which will enable a slight predetermined and controlled leakage.

As illustrated in FIGURE 4, the valve 22 comprises a disc which is connected by a stem 22b with the temperature responsive element 22a and is held by the latter, when the temperature of the fluid coolant upstream of the valve 22 is less than a predetermined minimum, closely against a valve seat plate 22c at the top of the valve cage 2201, thereby to close orifice 22e in plate 220 and to prevent coolant flow from system 18 into hose 19 and radiator 20, except as explained below.

In order to refine the operation of the structure described and to compensate for initial heating of manifold 50 prior to the initial opening of orifice 222 by the unseating of valve 22 from plate 220, a small controlled flow of coolant from system 18 into hose 19 is permitted by means of a restricted bleed port 22 through valve 22. Thus as the coolant upstream of valve 22 initially begins to warm, a slight flow of this coolant 6 into hose 19 and a warming of the inlet air in duct 35, 36 to thermostat element 30 is enabled. The tension in the latter urging choke valve 26 closed is thereby relaxed slightly and the enrichment of the fuel-air mixture will be decreased to correspond to the correspondingly warmer temperature of manifold 50.

I claim:

1. In an internal combustion engine, a fuel charging system having an air inlet conduit, a choke valve in said conduit, temperature responsive biasing means for adjusting said choke valve, an engine fluid cooling system including coolant duct means for circulating coolant in heat exchange relationship with said engine to cool the latter and also including a heat exchanger in series with said coolant duct means to receive heated coolant therefrom for cooling the latter, temperature responsive valve means responsive to the temperature of said engine for controlling the flow of coolant through said heat exchanger, an air heating duct having an inlet for receiving fresh air and having a portion in heat exchange relationship with the heated coolant fiowing into the hot side of said heat exchanger to heat the air in said heating duct, said heating duct also having a portion in heat exchange relationship with said temperature responsive biasing means to heat the latter by heated air from said heating duct.

2. In an internal combustion engine, a fuel charging system having an air inlet conduit, a choke valve in said conduit, temperature responsive biasing means for adjusting said choke valve, an engine fluid cooling system including coolant duct means for circulating coolant in heat exchange relationship with said engine to cool the latter and also including a heat exchanger in series with said coolant duct means to receive heated coolant therefrom for cooling the latter, temperature responsive valve means responsive to the temperature of said engine for controlling the flow of coolant through said heat exchanger, an air heating duct having an inlet for receiving fresh air and having a portion in heat exchange relationship with the heated coolant flowing into the hot side of said heat exchanger to heat the air in said heating duct, said heating duct also having a portion in heat exchange relationship with said temperature responsive biasing means to heat the later by heated air from said heating duct, and means for discharging said heated air from said biasing means into said air inlet conduit.

3. In an internal combustion engine, a fuel charging system having an air inlet conduit, a choke valve in said conduit, temperature responsive biasing means for adjusting said choke valve, an engine fluid cooling system including coolant duct means for circulating coolant in heat exchange relationship with said engine to cool the latter and also including a heat exchanger in series with said coolant duct means to receive heated coolant therefrom for cooling the latter, temperature responsive valve means responsive to the temperature of said engine for controlling the flow of coolant through said heat exchanger, means for supplying heated air to said air inlet conduit comprising an air heating duct having an inlet for receiving fresh air, an intermediate portion in heat exchange relationship with the heated coolant flowing into the hot side of said heat exchanger to heat the air in said heating duct, and an outlet discharging said heated air into said air inlet conduit, the resistance to air flow of said heating duct being determined so that the total heated air therefrom discharged into said air inlet conduit is less than approximately 15% of the total air flow in said air inlet duct during engine idle conditions, and said temperature responsive biasing means being in heat exchange relationship with the heated air in said heating duct to be heated thereby.

4. In an internal combustion engine, a fuel charging system having an air inlet conduit, a choke valve in said conduit, temperature responsive biasing means for adjusting said choke valve, an engine fluid cooling system including coolant duct means having an inlet and an outlet for circulating coolant in heat exchange relationship with said engine to cool the latter, a heat exchanger having an inlet and an outlet, a first conduit connecting the outlet of said coolant duct means with the inlet of said heat exchanger to supply heated coolant thereto to cool the latter, a second conduit connecting the outlet of said heat exchanger with the inlet of said coolant duct means to supply cooled coolant thereto, temperature responsive valve means for controlling the flow of coolant in said first conduit at a location adjacent the outlet of said coolant duct means, said valve means being responsive to the temperature of the heated coolant in said coolant duct means upstream of said location, an air heating duct having an inlet for receiving fresh air and also having an intermediate portion in heat exchange relationship with the coolant in said first conduit downstream of said location to heat the air in said heating duct, said heating duct also having a portion downstream thereof from said intermediate portion in heat exchange relationship with said temperature responsive biasing means to heat the latter by the heated air from said heating duct.

5. In an internal combustion engine, a fuel charging system having an air inlet conduit, a choke valve in said conduit, temperature responsive biasing means for adjusting said choke valve, an engine fluid cooling system including coolant duct means having an inlet and an outlet for circulating coolant inheat exchange relationship with said engine to cool the latter, a heat exchanger having an inlet and an outlet, a first conduit connecting the outlet of said coolant duct means with the inlet of said heat exchanger to supply heated coolant thereto to cool the latter, a second conduit connecting the outlet of said heat exchanger with the inlet of said coolant duct means to supply cooled coolant thereto, temperature responsive valve means for controlling the flow of coolant in said first conduit at a location adjacent the outlet of said coolant duct means, said valve means being responsive to the temperature of the heated coolant in said coolant duct means upstream of said location, means for supplying heated air to said air inlet conduit comprising an air heating duct having an inlet for receiving fresh air, an intermediate portion in heat exchange relationship with the heated coolant flowing in said first conduit downstream of said location to heat the air in said heating duct, and an outlet discharging said heated air into said air inlet conduit, said heating duct also having a portion downstream thereof from said intermediate portion in heat exchange relationship with said temperature responsive biasing means to heat the latter by the heated air from said heating duct.

6. In an internal combustion engine, a fuel charging system having an air inlet conduit, a choke valve in said conduit, temperature responsive biasing means for adjusting said choke valve, an engine fluid cooling system including coolant duct means in heat exchange relationship with said engine and having an inlet and outlet, at coolant pump in said inlet for circulating fluid coolant through said coolant duct means to cool said engine, a restricted bypass for said pump connecting said outlet with said inlet upstream of said pump, a heat exchanger in series with the outlet from said coolant duct means to receive heated coolant therefrom for cooling the latter, temperature responsive valve means for controlling the flow of heated coolant to said heat exchanger at a location downstream of said outlet and the latters connection with said bypass and being responsive to the temperature of said coolant upstream of said location, an air heating duct having an inlet for receiving fresh air and having a portion in heat exchange relationship with the heated coolant flowing into the hot side of said heat exchanger downstream of said location to heat the air in said heating duct, said heating duct also having a portion in heat exchange relationship with said temperature responsive biasing means to heat the latter by heated air from said heating duct.

7. In an internal combustion engine, a fuel charging system having an air inlet conduit, a choke valve in said conduit, temperature responsive biasing means for adjusting said choke valve, an engine fluid cooling system including coolant duct means in heat exchange relationship with said engine and having an inlet and outlet, a coolant pump in said inlet for circulating fluid coolant through said coolant duct means to cool said engine, a restricted bypass for said pump connecting said outlet with said inlet upstream of said pump, a heat exchanger in series with the outlet from said coolant duct means to receive heated coolant therefrom for cooling the latter, temperature responsive valve means for controlling the flow of heated coolant to said heat exchanger at a location downstream of said outlet and the latters connection with said bypass and being responsive to the temperature of said coolant upstream of said location, means for supplying heated air to said air inlet conduit comprising an air heating duct having an inlet for receiving fresh air, an intermediate portion in heat exchange relationship with the heated coolant flowing into said heat exchanger downstream of said valve means to heat the air in said heating duct, and an outlet discharging said heated air into said air inlet conduit, said temperature responsive biasing means being responsive to the temperature of the air in said heating duct downstream thereof from said intermediate portion.

8. In an internal combustion engine, a fuel charging system having an air inlet conduit, a choke valve in said conduit, temperature responsive biasing means for adjusting said choke valve, an engine fluid cooling system ineluding coolant duct means for circulating fluid coolant in heat exchange relationship with said engine to cool the latter, a pump for circulating said coolant through said coolant duct means, a restricted bypass for said pump connecting the outlet of said coolant duct means with the inlet of said pump to supply coolant thereto, a heat exchanger having an outlet in communication with the inlet of said pump, a coupling conduit connecting the outlet of said coolant duct means and the inlet of said heat exchanger for supplying heated coolant thereto to be cooled, valve means in said coupling conduit at a location adjacent the outlet of said coolant duct means for controlling the flow of coolant in said coupling conduit to said heat exchanger, means responsive to the temperature of the heated coolant in said coolant duct means upstream of said valve means for opening the latter to increase the coolant flow in said coupling conduit as said temperature increases, an air heating duct having an opening for receiving fresh air, one portion of said air heating duct being in heat exchange relationship with the coolant in said coupling conduit downstream of said valve means to heat the air in said air heating duct, a second portion of said air heating duct being in communication with said temperature responsive biasing means to heat the latter by the heated air in said air heating duct.

9. In an internal combustion engine, a fuel charging system having an air inlet conduit, a choke valve in said conduit, temperature responsive biasing means for adjusting said choke valve, an engine fluid cooling system including coolant duct means for circulating fluid coolant in heat exchange relationship with said engine to cool the latter, a pump for circulating said coolant through said coolant duct means, a restricted bypass for said pump connecting the outlet of said coolant duct means with the inlet of said pump to supply coolant thereto, a heat exchanger having an outlet in communication with the inlet of said pump, a coupling conduit connecting the outlet of said coolant duct means and the inlet of said heat exchanger for supplying heated coolant thereto to be cooled, valve means in said coupling conduit at a location adjacent the outlet of said coolant duct means for controlling the flow of coolant in said coupling conduit to said heat exchanger, means responsive to the temperature of the heated coolant in said coolant duct means upstream of said valve means for opening the latter to increase the coolant flow in said coupling conduit as said temperature increases, means for supplying heated air to said air inlet conduit comprising an air heating duct having an opening for receiving fresh air, a first part in heat exchange relationship with the coolant in said coupling conduit downstream of said valve means to heat the air in said air heating duct, a second part in heat exchange relationship with said temperature responsive biasing means to heat the latter by the heater air in said air heating duct, and an outlet discharging said heated air into said air inlet conduit.

10. The combination according to claim 9 wherein the resistance to air flow of said air heating duct is determined so that the total heated air discharged therefrom into said air inlet conduit is less than approximately 15% of the total air flow in said air inlet duct during engine idle conditions.

11. In an internal combustion engine, a fuel charging system having an air inlet conduit, a choke valve in said conduit, coolant duct means for circulating fluid coolant in heat exchange relationship with said engine to cool the latter, a heat exchanger having an outlet in communication with the inlet of said coolant duct means, a coupling conduit connecting the outlet of said coolant duct means and the inlet of said heat exchanger for supplying heated coolant thereto to be cooled, valve means in said coupling conduit at a location adjacent the outlet of said coolant duct means for controlling the flow of coolant in said coupling conduit to said heat exchanger, means responsive to the temperature of the heated coolant in said coolant duct means upstream of said valve means for opening the latter to increase the coolant flow in said coupling conduit as said temperature increases, and temperature responsive biasing means responsive to the temperature of the coolant in said coupling conduit for adjusting said choke valve.

12. The combination according to claim 11 wherein said valve means is normally urged to its closed condition by said means responsive to the temperature of the heated coolant in said coolant duct means when said coolant is at less than a predetermined temperature, and including means to enable a controlled leakage of coolant from said coolant duct means into said coupling conduit to cause an initial heating of the air in said air heating duct prior to opening of said valve means in response to the coolant in said coolant duct means at said predetermined temperature.

No references cited. 

